Ureter drain tubes are used when a disease of the ureter connecting the kidney to the bladder hampers urine passage The drain tube assures urine elimination from the kidney. By means of an endoscope inserted through the urethra into the bladder, such a drain tube is advanced from the bladder through the ureter as far as the kidney and, as a rule, is designed in such a way that its ends lie respectively in the kidney and in the bladder and are held in place by their ends which are curved to prevent shifting. Apertures are provided at both ends to assure urine passage. Ureter drain tubes take the form of soft tubes a few millimeters in diameter.
To be insertable, these soft tubes are stiffened by an inserted, less flexible mandrin (wire or spiral-wire tube or combination of both) until reliable advancing without danger of kinking is possible, even through constrictions in the ureter.
Problems arise when multiple advancing and retraction is required at a ureter constriction in order to seek a suitable passageway.
Because the drain catheter length essentially is only enough for the distance from kidney to bladder, that is, the length is insufficient to pass through the inserting endoscope as far as the outside, an advancing tube always must be employed to allow advancing the drain tube. This advancing tube also is seated on the mandrin. The cited problems arise when retraction is desired outside of the endoscope. Neither retraction of the advancing tube nor retraction of the mandrin can be relied upon to pull back the possibly jammed drain tube. In the older state of the art, the drain can only be advanced, not retracted.
German Gebrauchsmuster 86 14 013.2 discloses a design wherein the advancing tube communicates through a perforation with the ureter drain. This perforation allows advancing and retracting when the ureter drain is inserted by appropriate manipulation by means of the communication. Following proper emplacement of the ureter drain, the perforation must be removed. For that purpose the advancing tube and the mandrin are pulled in opposite directions, the mandrin resting against the distal tip of the ureter drain which may be closed. The pull is hard enough to tear the perforation.
A similar design is known from German Offenlegungsschrift 33 39 179 where the ureter drain also may be distally open. In this instance the endoscope, illustratively a suitable forceps, holds the ureter drain and the advancing hose then is pulled until the perforation tears.
However, such designs incur a series of drawbacks. It is difficult to manufacture the perforation such that it can withstand manipulation but will tear when desired. Because of inaccuracies of manufacture, it happens frequently that the perforation will not tear unless forces be applied which are great enough to entail danger of injury. Moreover, the irregularities of the perforation site may prove bothersome at the proximal end of the ureter drain at the bladder, and irritation may result when resting against the bladder wall. Moreover, the known devices require either a forceps to hold the ureter drain or a closed ureter drain end against which the mandrin rests. Limitations in design or construction result, which lead to problems
The two above designs suffer from another restriction in practice in that while the ureter drain and the advancing tube are connected during manipulation, the mandrin on the other hand must be kept in its position to prevent it from slipping out. This is the reason that as a rule the proximal end of the advancing tube is clamped to the mandrin. The presence of this clamp necessitates additional manual operations when being applied or detached.
A ureter drain of the initially described kind is described in the published German Offenlegungsschrift 37 14 839 (published after the priority date of the present application). It does solve the problems of the cited earlier state of the art. The neck at the end of the advancing tube is inserted into the proximal end of the ureter drain and is clamped to the guide advanced by the advancing tube as far as into the ureter drain. Enough clamping force is generated thereby for the required manipulations of advancing and retraction to hold the advancing hose to the ureter drain. If now the ureter drain is properly emplaced in the body, then the end of the advancing tube projecting externally from the patient can be held in place and the guide retracted as far as over the clamping site. Thereby, the clamping is removed and the advancing tube can be pulled out.
Nevertheless this design incurs the drawback of difficult assembly when setting up the clamping. This work is carried out away from the patient, preferably at the factory, so that the ureter drain is furnished to the physician as a finished operable unit, where the guide is clamped to the advancing tube.
In the design shown in German Offenlegungsschrift 37 14 839, the neck of the advancing tube is in the shape of a sector of tube and is asymmetrically located to one side of the tube axis. In the presence of clamping, the mandrin itself rests with one side against the inside of the ureter drain and the other side against the neck. If during assembly the neck already has been inserted into the ureter drain and next the mandrin is advanced to achieve clamping, then the mandrin rubs on one side against the neck and on the other side against the ureter drain also and, upon further insertion into the ureter drain, attempts to move it forward by friction, that is away from the advancing tube. To prevent this from happening, the ureter drain must be kept stationary relative to the advancing tube using two hands, while the mandrin is advanced using a third hand. Accordingly, assembly by one person is quite difficult.